As the magnetron is generally capable of generating high-frequency output efficiently, it is widely used for a radar apparatus, medical equipment, cooking apparatuses such as a microwave oven, semiconductor manufacturing equipment and other fields such as microwave application devices. High-output microwaves are required for the semiconductor manufacturing equipment and for industrial heating. In such cases, it is necessary to improve cooling performance of the magnetron so as to correspond to the output of microwaves, therefore, it is necessary to increase cooling ability. However, the increase in cooling ability leads to the size increase of the magnetron, which causes increase of a space for housing the magnetron and increase of the device itself, therefore, a small-sized magnetron having a cooling structure with excellent performance is required.
In Patent Literature 1, a magnetron having a cooling block is described, which is closely disposed on an outer wall of an anode cylinder and has plural flow paths for a cooling medium (hereinafter referred to as a refrigerant) thereinside along a tube axis direction of the anode cylinder.